Ruminants require fiber or roughage to ensure proper function of the rumen, a modified part of the stomach wherein bacteria digest cellulose from plants into usable nutrients. Rumination is a process which permits an herbivore to forage and ingest food rapidly, then complete the chewing at a later time. They need peace and quiet to ruminate. Healthy sheep and goats spend a third of their life, ruminating, which is belching up a ball of grass from the stomach, chewing it and then swallowing it again (commonly called, "chewing their cud").

It is of considerable practical importance that the size and length of ruminal papillae respond to concentrations of VFA's in the rumen. Animals that have been on a high plane of nutrition, with abundant VFA production, have long, luxuriant papillae well suited to promote absorption. In contrast, animals which have been under nutritional deprivation have small, blunted papillae, and require time on a high quality diet to allow for development of their papillae and absorptive capacity.

VFA - Volatile fatty acids are produced in large amounts through ruminal fermentation and are of paramount importance in that they provide greater than 70% of the ruminant's energy supply.

Sheep are ruminants–– even-toed animals with four stomachs. Why four? As you might guess, the leaves, stems, grasses and weeds that sheep chow-down on are extremely difficult to digest. When a sheep eats, the food goes into the first stomach, called the rumen where it is stored. From there, it moves gradually into the reticulum where it is broken down by bacteria and acid to form cud—the stuff you see cattle, deer and sheep endlessly chewing. Muscles in the reticulum push the cud into the sheep’s mouth for a good second chewing to help break down the stems and leaves even further. Once the sheep swallows the cud it enters the omasum for a little more digestion before making its last stomach-stop—the abomasums--where it is mixed with acids before finally entering the intestine. Above Information from "Sheep Eats" PSNH